U.S. patent number 9,528,037 [Application Number 14/261,882] was granted by the patent office on 2016-12-27 for method for selecting lubricants for heat pumps.
This patent grant is currently assigned to HONEYWELL INTERNATIONAL INC.. The grantee listed for this patent is HONEYWELL INTERNATIONAL INC.. Invention is credited to Christopher J. Seeton, Mark W. Spatz, Raymond H. Thomas, David P. Wilson, Samuel F. Yana Motta.
United States Patent |
9,528,037 |
Thomas , et al. |
December 27, 2016 |
Method for selecting lubricants for heat pumps
Abstract
Provided is a method for selecting a lubricant and a refrigerant
for use in a vapor-compression refrigeration device such that the
combination of the lubricant and refrigerant produces a fluid
system having a lubricant-rich phase and a refrigerant-rich phase,
yet exhibits miscible-type properties.
Inventors: |
Thomas; Raymond H. (Pendleton,
NY), Seeton; Christopher J. (East Amherst, NY), Wilson;
David P. (East Amherst, NY), Yana Motta; Samuel F. (East
Amherst, NY), Spatz; Mark W. (East Amherst, NY) |
Applicant: |
Name |
City |
State |
Country |
Type |
HONEYWELL INTERNATIONAL INC. |
Morristown |
NJ |
US |
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Assignee: |
HONEYWELL INTERNATIONAL INC.
(Morris Plains, NJ)
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Family
ID: |
41115077 |
Appl.
No.: |
14/261,882 |
Filed: |
April 25, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140230465 A1 |
Aug 21, 2014 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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13666166 |
Nov 1, 2012 |
8739559 |
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12416734 |
Dec 4, 2012 |
8322149 |
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61041474 |
Apr 1, 2008 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B
45/00 (20130101); F25B 31/002 (20130101); C10M
171/008 (20130101); C09K 5/044 (20130101); C09K
5/045 (20130101); C10N 2030/70 (20200501); C10N
2020/101 (20200501); C09K 2205/24 (20130101); C10N
2030/06 (20130101); C10M 2207/2835 (20130101); C10N
2040/30 (20130101); C10M 2209/1033 (20130101); C10M
2209/1085 (20130101); C09K 2205/126 (20130101) |
Current International
Class: |
F25B
43/02 (20060101); C09K 5/04 (20060101); C10M
171/00 (20060101); F25B 31/00 (20060101); F25B
45/00 (20060101) |
Field of
Search: |
;62/84,498,56,192 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Jones; Melvin
Attorney, Agent or Firm: Szuch; Colleen D.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a Continuation of U.S. application Ser. No.
13/666,166, filed Nov. 1, 2012, which is a Divisional of U.S.
application Ser. No. 12/416,734, filed Apr. 1, 2009 (now U.S. Pat.
No. 8,322,149), which claims the priority benefit of U.S.
Provisional Application No. 61/041,474, filed Apr. 1, 2008, and
U.S. Provisional Application No. 61/043,486, filed Apr. 9, 2008,
each of which are incorporated herein by reference in their
entirety.
Claims
What is claimed is:
1. A vapor compression system comprising: a condenser having an
inlet side and an outlet side; a compressor having an inlet side
and an outlet side; an evaporator having an inlet side and an
outlet side; an expansion valve having an inlet side and an outlet
side; a circulation loop placing each of the condenser, compressor,
evaporator, and expansion valve into fluid communication; and a
heat transfer fluid comprising a refrigerant-rich portion and a
lubricant-rich portion, wherein a relative difference between the
densities of the portions is less than 20%, and wherein at a
temperature below a phase inversion temperature of the heat
transfer fluid the refrigerant-rich portion and the lubricant-rich
portion are immiscible and one of the refrigerant-rich portion and
lubricant-rich portion is more dense and at a temperature above the
phase inversion temperature the refrigerant-rich portion and the
lubricant-rich portion are immiscible and the other of the
refrigerant-rich portion and the lubricant-rich portion is more
dense.
2. The system of claim 1 wherein at a temperature below the phase
inversion temperature the refrigerant-rich portion is more dense
than the lubricant-rich portion and at a temperature above the
phase inversion temperature the lubricant-rich portion is more
dense than the refrigerant-rich portion.
3. The system of claim 1 wherein the refrigerant-rich portion
comprises at least one C.sub.2 to C.sub.5 fluoroalkene.
4. The system of claim 3 wherein the fluoroalkene is a C.sub.3 or
C.sub.4 fluoroalkene.
5. The system of claim 3 wherein the fluoroalkene has a formula
XCF.sub.zR.sub.3-z wherein X is a substituted or unsubstituted
vinyl or allyl radical, R is independently Cl, Br, I or H, and z is
1 to 3.
6. The system of claim 5 wherein z is 3.
7. The system of claim 3 wherein the fluoroalkene is selected from
the group consisting of trifluorpropene, tetrafluoropropene, and
pentafluoropropene.
8. The system of claim 7 wherein the fluoroalkene is selected from
the group consisting of cis-1,3,3,3-tetrafluoropropene;
trans-1,3,3,3-tetrafluoropropene; 1,1,1,2-tetrafluoropropene;
1,1,1-trifluoro-3-chloro-2-propene; 3,3,3-trifluoropropene; and
combinations thereof.
9. The system of claim 1 wherein the lubricant-rich portion
comprises a lubricant selected from the group consisting of at
least one of a one polyol ester, a polyalkylene glycol, a
polyalkylene glycol ester, mineral oils, alkylbenzenes,
polyalpha-olefins, alkylated naphthalenes, and polyalkylene glycol
esters.
10. The system of claim 1 wherein the lubricant-rich portion
comprises a lubricant selected from the group consisting of at
least one of a one polyol ester, a polyalkylene glycol, and a
polyalkylene glycol ester.
11. The system of claim 10 wherein said polyalkylene glycol is a
branched or straight chain polymer having from about 5 to about 50
units of oxyethylene, oxypropylene, oxybutylene, oxypentylene, or
combinations thereof.
12. The system of claim 11 wherein said polymer comprises at least
50 weight percent oxypropylene units.
13. The system of claim 10 wherein said polyol ester has a
structure according to formulae I or II:
RO(R.sup.1O).sub.nC(O)R.sup.2 (I) R.sup.3(O)C(O)R.sup.2 (II)
wherein R is a hydrocarbyl group having at least 2 carbon atoms,
R.sup.1 is a hydrocarbylene group, R.sup.2 is H, hydrocarbyl,
--CF.sub.3, --R.sup.4CN, --R.sup.4NO.sup.2 or
R.sup.5OCH(R.sup.6)--, R.sup.3 is a --R.sup.4CF.sup.3, --R.sup.4CN
or --R.sup.4NO.sub.2 group, provided that R.sup.3 may be a
hydrocarbyl group when R.sup.2 is --R.sub.4CN, n is an integer from
1 to about 50, R.sup.4 is a hydrocarbylene group, R.sup.5 is H, a
lower hydrocarbyl group or R.sup.7C(O)-- where R.sup.7 is a
hydrocarbyl group, and R.sup.6 is H or a lower hydrocarbyl
group.
14. The system of claim 1 wherein the relative difference between
the densities of the portions is less than 10%.
15. The system of claim 1 wherein the relative difference between
the densities of the portions is less than 5%.
16. The system of claim 1 wherein said temperature above said phase
inversion temperature is between about +30.degree. C. to about
+75.degree. C.
17. The system of claim 1 wherein said temperature below said phase
inversion temperature is between about -40.degree. C. to about
+25.degree. C.
18. The system of claim 1 wherein the composition comprises from
about 60 to about 90 weight percent of the refrigerant-rich portion
and from about 10 to about 40 weight percent of the lubricant-rich
portion, wherein weight percents are relative to the total weight
of said composition.
19. The system of claim 1 wherein the composition comprises from
about 70 to about 99 weight percent of the refrigerant-rich portion
and from about 1 to about 30 weight percent of the lubricant-rich
portion, wherein weight percents are relative to the total weight
of said composition.
20. The system of claim 1 wherein said composition further
comprises one or more of extreme pressure additives, anti-wear
additives, oxidation stabilizers, thermal stabilizers, pour and
floc point depressants, anti-foaming agents, lubricants soluble in
fluoroolefins, surfactants, compatibilizers, and solubilizing
agents.
Description
BACKGROUND
1. Field of Invention
The present invention relates to methods for selecting lubricants
used in heat pumps. More particularly, the invention relates to
methods used to select lubricants and hydrofluoroolefins
refrigerant combinations for use in compressor-type heat pumps.
2. Description of Prior Art
The use of chlorine-containing refrigerants, such as
chlorofluorocarbons (CFC's) and hydrochlorofluorocarbons (HCFC's),
in a compression-type refrigeration device (e.g., heat pumps, air
conditioners, refrigerators, and the like) is disfavored because
these refrigerants can damage the Earth's ozone if they leak or are
otherwise discharged from the device. Accordingly, it is desirable
to retrofit chlorine-containing refrigeration systems by replacing
chlorine-containing refrigerants with non-chlorine-containing
refrigerant compounds that will not deplete the ozone layer, such
as hydrofluoroalkanes (HFCs) or hydrofluoroolefins (HFOs). Of
these, HFOs are more desirable because they are typically
characterized as having a much lower Global Warming Potential
(GWP).
Preferably, these replacement refrigerants are compatible (e.g.,
miscible) with conventional compression-type refrigeration device
lubricants. Such compatibility allows lubricant to flow more easily
with the refrigerant throughout the system thereby increasing the
system's efficiency and expected life span. The lack of
compatibility can result in separation of the refrigerant and
lubricant into different phases. If phase separation occurs between
the refrigerant and lubricant while the refrigerator is running, it
affects the life and efficiency of the apparatus seriously. For
example, if phase separation of the refrigerant and the lubricating
oil occurs in the compressor, the moving parts would be
inadequately lubricated, resulting in seizure or other troubles and
thereby the life of apparatus is shortened considerably. If phase
separation occurs in the evaporator, a lubricating oil having high
viscosity exists and thereby the efficiency of heat exchange is
decreased. Unfortunately, many non-chlorine-containing
refrigeration fluids, including HFCs and HFOs, are relatively
insoluble and/or immiscible in conventional lubricants, including,
for example, mineral oils, alkylbenzenes or polyalpha-olefins. In
order for a refrigeration fluid-lubricant combination to work
efficiently within a compression refrigeration, air-conditioning or
heat pump system, the lubricant is preferably compatible with a
refrigerant over a wide range of operating temperatures.
Generally, a compression-type refrigeration device is composed of a
compressor, a condenser, expansion valve, and an evaporator, having
a mechanism wherein the mixture of a refrigerant and a lubricating
oil is circulating in the closed system. In said compression-type
refrigeration device, though it depends on the kind of apparatus,
generally the temperature in the compressor rises to about
50.degree. C. or higher, while in the cooler, the temperature comes
to be about -40.degree. C. Accordingly, the refrigerant and the
lubricating oil must circulate in this system without phase
separation usually in the range of about -40.degree. to +50.degree.
C. (See, e.g., U.S. Pat. No. 5,536,881, which is incorporated
herein by reference.)
Accordingly, the selection of a lubricant for a compression-type
refrigeration device should include an analysis of the lubricant's
miscibility with the desired refrigerant. Achieving miscibility
reduces the need for an oil separator, which can be installed
immediately after the compressor to capture immiscible oil and
return it to the compressor to maintain a desired level of
lubrication. Maintaining good lubrication reduces problems
associated with low oil return, including fouling of the heat
exchanger surfaces and burn-out of the compressor. However, as
noted above, many desirable HFC and HFO refrigerant are immiscible
in conventional lubricants at room temperature. Although various
mixtures of HFO and lubricants are known (see, e.g., US Patent
Application Publication No. 2004/00898, which is incorporated
herein by reference in its entirety), there remains a need for a
method of selecting a lubricant that is compatible with HFC, and
particularly HFO, refrigerants.
SUMMARY OF THE INVENTION
It has been surprisingly found that certain refrigerant/lubricant
combinations used in compression-type refrigeration devices did not
result in oil return problems, despite the lack of miscibility
between the refrigerant and lubricant. For example, a fluid system
comprising certain HFO refrigerants and certain lubricants have
been found to exhibit a miscible-type property during the operation
of a compression-type refrigeration devices even though the
refrigerant and lubricant form two phases at the upper operating
temperature of the device and also at lower operating
temperatures.
As used herein, the term "upper operating temperature" means the
temperature of the refrigerant at the outlet of the condenser
during normal device operation and is generally between about
+30.degree. C. and about +75.degree. C., and preferably about
+40.degree. C. to about +50.degree. C. The term "lower operating
temperature" means the temperature of the refrigerant at the outlet
of the expansion value during normal device operation and is
generally between about -40.degree. C. to about +25.degree. C. In
certain preferred embodiments, particularly for embodiments wherein
the device is refrigeration equipment, the lower operating
temperature is in a range of -40 to -5.degree. C. In certain other
preferred embodiments, particularly for embodiments wherein the
device is a refrigerator or heat pump, the lower operating
temperature is in a range of about -20 to +5.degree. C. In certain
other preferred embodiments, particularly for embodiments wherein
the device is an air conditioner, the lower operating temperature
is in a range of about 0 to +15.degree. C.
As used herein, the term "phase" means a compositional region of a
fluid system that is substantially chemically uniform and
physically distinct. The phase size may be microscopic or, more
preferably, macroscopic.
The term "lubricant" means a substance that when disposed between
two moving surfaces, tends to reduce the friction between the
surfaces, thereby improving efficiency and reducing wear.
Lubricants may optionally have the function of dissolving and/or
transporting foreign particles in a device.
The term "refrigerant" means one or more compounds that undergo a
phase change from a gas to a liquid and back in a conventional
compression-type refrigeration device to effectively transfer heat
to or from an environment.
The term "lubricant-rich phase" means a phase in a fluid system
comprising a majority of lubricant relative to refrigerant (i.e.,
more than about 50 weight % and less than 100 weight %). In certain
embodiments, the lubricant-rich phase comprises from about 10 to
about 90 wt. % lubricant relative to refrigerant, more preferably
about 25 to about 70 wt. %, and even more preferably about 40 to
about 60 wt %.
The term "refrigerant-rich phase" means a phase in a fluid system
comprising a majority of refrigerant (i.e., more than about 50
weight % and less than 100 weight %), preferably at least about 75
wt. % to less than 100 wt. % refrigerant relative to lubricant, and
more preferably at least about 90 to about 98 wt. % refrigerant
relative to lubricant.
With respect to a fluid system comprising a refrigerant-rich phase
and a lubricant-rich phase, inversion of the phases occurs as the
density of each phase inversely changes with respect to a change in
temperature, i.e., a first phase that is more dense with respect to
a second phase at one temperature changes to become less dense
compared to the second phase as a different temperature. More
particularly, at relatively low temperatures, the refrigerant-rich
phase is denser than the lubricant-rich phase and, accordingly,
settles to the bottom of the fluid system. As the temperature
rises, the lubricant-rich phase becomes heavier and sinks to the
bottom. This phase inversion is believed to produce the
miscible-type characteristic observed in the fluid system.
Lubricant return to the compressor is therefore improved.
Accordingly, an aspect of the invention is a method for selecting a
refrigerant and lubricant for a vapor-compression refrigeration
device system comprising the steps of: (a) determining a lower
operating temperature range of a vapor-compression refrigeration
device; (b) determining an upper operating temperature range of the
vapor-compression refrigeration device; and (c) selecting a
refrigerant comprising at least one C.sub.2 to C.sub.5 fluoroalkene
at a first concentration and selecting a lubricant comprising at
least one polyol ester, polyalkylene glycol, or polyalkylene glycol
ester at a second concentration to produce a fluid system having a
refrigerant-rich phase and a lubricant-rich phase at a first
temperature within said lower operating temperature range and at a
second temperature within said upper operating temperature range
provided that said second temperature is higher than said first
temperature, wherein the refrigerant-rich phase is denser relative
to the lubricant-rich phase at said first temperature and wherein
the lubricant-rich phase is denser relative to the refrigerant-rich
phase at said second temperature, provided that the relative
difference in densities between the two phases is less than 20% at
said first temperature and less than 20% at said second
temperature.
In another aspect of the invention, provided is a method for
introducing a refrigerant and lubricant into a vapor-compression
refrigeration device system comprising the steps of: (a) providing
a vapor-compression refrigeration device comprising a heat transfer
circuit, a compressor having an inlet side and an outlet side, and
refrigerant and lubricant reservoir, wherein said reservoir is in
fluid communication with the inlet side of the compressor and with
said heat transfer circuit, and said heat transfer circuit is in
fluid communication with said outlet side of the compressor; (b)
determining the lower operating temperature range of the
vapor-compression refrigeration device; (c) determining the upper
operating temperature range of the vapor-compression refrigeration
device; (d) selecting a refrigerant comprising at least one C.sub.2
to C.sub.5 fluoroalkene at a first concentration and selecting a
lubricant comprising at least one polyol ester or polyalkylene
glycol at a second concentration to produce a fluid system having a
refrigerant-rich phase and a lubricant-rich phase at a first
temperature within said lower operating temperature range and at a
second temperature within said upper operating temperature range
provided that said second temperature is higher than said first
temperature, wherein the refrigerant-rich phase is denser relative
to the lubricant-rich phase at said first temperature and wherein
the lubricant-rich phase is denser relative to the refrigerant-rich
phase at said second temperature; and (e) introducing said
refrigerant and lubricant into the vapor-compression refrigeration
device.
In yet another aspect of the invention, provided is a method for
lubricating a vapor-compression refrigeration device system
comprising the steps of: (a) providing a vapor-compression
refrigeration device comprising a heat transfer circuit, a
compressor having an inlet side and an outlet side, and refrigerant
and lubricant reservoir, wherein said reservoir is in fluid
communication with the inlet side of the compressor and with said
heat transfer circuit, and said heat transfer circuit is in fluid
communication with said outlet side of the compressor; (b)
determining the lower operating temperature range of the
vapor-compression refrigeration device; (c) determining the upper
operating temperature range of the vapor-compression refrigeration
device; (d) selecting a refrigerant comprising at least one C.sub.2
to C.sub.5 fluoroalkene at a first concentration and selecting a
lubricant comprising at least one polyol ester or polyalkylene
glycol at a second concentration to produce a fluid system having a
refrigerant-rich phase and a lubricant-rich phase at a first
temperature within said lower operating temperature range and at a
second temperature within said upper operating temperature range
provided that said second temperature is higher than said first
temperature, wherein the refrigerant-rich phase is denser relative
to the lubricant-rich phase at said first temperature and wherein
the lubricant-rich phase is denser relative to the refrigerant-rich
phase at said second temperature; (e) introducing said refrigerant
and lubricant into the vapor-compression refrigeration device at
said first temperature; and (f) lubricating said vapor-compression
refrigeration device with said lubricant, wherein said lubricating
involves increasing the temperature of the vapor-compression
refrigeration device to produce an inversion of the refrigerant and
lubricant-rich phases.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a graph of the density of the polyalkylene glycol
lubricant ND 8 oil with HFO-1234yf.
FIG. 2 shows a graph of the density of the polyalkylene glycol
lubricant Idemitsu PAG 46PS with HFO-1234yf.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
Preferred embodiments of the invention involve the selection of a
fluoroalkene refrigerant and a lubricant which, when combined,
produce a fluid system having a miscible-type property. Such a
fluid system is useful in the operation of vapor-compression
refrigeration device.
Useful refrigerants preferably comprises at least one C.sub.2 to
C.sub.5 fluoroalkene, and more preferably a C.sub.3 to C.sub.4
fluoroalkene. Preferred fluoroalkenes are those having the formula:
XCF.sub.zR.sub.3-z wherein X is a substituted or unsubstituted
vinyl or allyl radical, R is independently Cl, Br, I or H, and z is
1 to 3, preferably 3. Particularly preferred fluoroalkanes include
trifluorpropenes, tetrafluoropropenes, and pentafluoropropenes.
Examples of preferred isomers of these compounds include
cis-1,3,3,3-tetrafluoropropene; trans-1,3,3,3-tetrafluoropropene;
1,1,1,2-tetrafluoropropene; 1,1,1-trifluoro-3-chloro-2-propene; and
3,3,3-trifluoropropene. The refrigerant can include one of these
compounds of some combination thereof.
Useful lubricants include polyol ester and polyalkylene glycols.
The polyalkylene glycol lubricants suitable for use with the
present invention typically contain from about 5 to 50 oxylakylene
repeating units that have from 1 to 5 carbon atoms. The
polyalkylene glycol can be straight chain or branched and can be a
homopolymer or co-polymer of 2, 3 or more oxyethylene,
oxypropylene, oxybutylene or oxypentylene groups or combinations
thereof in any proportions. Preferred polyalkylene glycols contain
at least 50% oxypropylene groups. Compositions according to the
present invention may contain one or more polyalkylene glycols as
the lubricant, one or more polyalkylene glycol esters as the
lubricant, one or more polyol esters as the lubricant, or a mixture
of one of more polyalkylene glycols, one or more polyalkylene
glycol esters and one or more polyol esters. Vinyl ethers are also
useful in this invention.
Useful polyalkylene glycols are described in U.S. Pat. Nos.
4,971,712; 4,948,525 and 5,254,280, and 4,755,316, the printed
specifications of which are incorporated herein by reference. While
suitable polyalkylene glycols include glycols terminating at each
end with a hydroxyl group, other suitable lubricants include
polyalkylene glycols in which either or both terminal hydroxyl
group is capped. The hydroxyl group may be capped with alkyl groups
containing from 1 to 10 carbon atoms, 1 to 10 carbon atom alkyl
groups containing heteroatoms such as nitrogen, the fluoroalkyl
groups described by U.S. Pat. No. 4,975,212, the printed
specification of which is incorporated herein by reference. When
both polyalkylene glycol hydroxyl groups are end capped, the same
type or a combination of two different types of terminal capping
groups can be used. Either or both hydroxyl groups can also be
capped by forming the ester thereof with a carboxylic acid as
disclosed by U.S. Pat. No. 5,008,028, the specification of which is
also incorporated herein by reference.
The carboxylic acid can also be fluorinated. When both ends of the
polyalkylene glycol are capped, either or both ends may be capped
with an ester, or one end may be capped with an ester and the other
not capped or capped with one of the aforementioned alkyl,
heteroalkyl or fluoroalkyl groups.
Commercially available polyalkylene glycol lubricants include
Goodwrench Refrigeration Oil for General Motors and MOPAR-56 from
Daimler-Chrysler, which is a polyalkylene glycol that is bis-capped
by acetyl groups. A wide variety of polyalkylene glycol lubricants
are also available from Dow Chemical or Shrieve Chemical Products.
Commercially available polyol esters include Mobil EAL Arctic 22CC
available from Exxon-Mobil and Solest 120 available from CPI
Engineering Services, Inc.
Preferred polyol esters have a structure according to formulae (I)
or (II): RO(R.sup.1O).sub.nC(O)R.sup.2 (Formula I)
R.sup.3(O)C(O)R.sup.2 (Formula II) wherein R is a hydrocarbyl group
having at least 2 carbon atoms, R.sup.1 is a hydrocarbylene group,
R.sup.2 is H, hydrocarbyl, --CF.sub.3, --R.sup.4CN,
--R.sup.4NO.sup.2 or R.sup.5OCH(R.sup.6)--, R.sup.3 is a
--R.sup.4CF.sup.3, --R.sup.4CN or --R.sup.4NO.sub.2 group, provided
that R.sup.3 may be a hydrocarbyl group when R.sup.2 is
--R.sub.4CN, n is an integer from 1 to about 50, R.sup.4 is a
hydrocarbylene group, R.sup.5 is H, a lower hydrocarbyl group or
R.sup.7C(O)-- where R.sup.7 is a hydrocarbyl group, and R.sup.6 is
H or a lower hydrocarbyl group.
These are more fully described in U.S. Pat. No. 5,008,028, the
printed specification of which is incorporated herein by reference.
Preferably the fluoroalkene and the lubricant are substantially
immiscible with one another.
The lubricants of this invention typically have a density of when
measured at a temperature of from about 25.degree. C. to about
50.degree. C. ranging from about 0.7 g/cm.sup.3 to about 1.2
g/cm.sup.3; preferably from about 0.9 g/cm.sup.3 to about 1
g/cm.sup.3; and more preferably from about 0.95 g/cm.sup.3 to about
1 g/cm.sup.3.
The fluoroalkenes of this invention typically have a density of
when measured at a temperature of from about 25.degree. C. to about
50.degree. C. ranging from about from about 0.8 g/cm.sup.3 to about
1.4 g/cm.sup.3; preferably from about 0.99 g/cm.sup.3 to about 1.09
g/cm.sup.3; and more preferably from about 1.04 g/cm.sup.3 to about
1.19 g/cm.sup.3.
In a typical automobile refrigeration system, the fluoroalkene may
be present in an amount of from about 60 to about 90 weight
percent, preferably from about 65 to about 80 weight percent based
on the weight of the total refrigerant and lubricant charge.
In a typical automobile refrigeration system, the lubricant may be
present in an amount of from about 10 to about 40 weight percent,
preferably from about 20 to about 35 weight percent based on the
weight of the total refrigerant and lubricant charge.
In a typical stationary refrigeration system, the fluoroalkene may
be present in an amount of from about 70 to about 99 weight
percent, preferably from about 80 to about 85 weight percent based
on the weight of the total refrigerant and lubricant charge.
In a typical stationary refrigeration system, the lubricant may be
present in an amount of from about 1 to about 30 weight percent,
preferably from about 15 to about 20 weight percent based on the
weight of the overall total refrigerant and lubricant charge.
In preferred embodiments, the refrigerant-lubricant mixture
compositions of this invention may have viscosities of from about 1
to 1000 centistokes at about 37.degree. C., more preferably in the
range of from about 2 to about 200 centistokes at about 37.degree.
C. and even more preferably of from about 4 to about 40 centistokes
at about 37.degree. C.
In addition to the HFO refrigerant and lubricant, compositions
according to the present invention can include other additives or
materials of the type used in refrigeration, air-conditioning and
heat pump compositions to enhance their performance. For example,
the compositions can also include extreme pressure and anti-wear
additives, oxidation and thermal stability improvers, pour and floc
point depressants, anti-foaming agents, other lubricants soluble
and insoluble in HFO's, and the like. Examples of such additives
are disclosed in U.S. Pat. No. 5,254,280, the printed specification
of which is incorporated herein by reference
Compositions of the present invention can thus further include a
quantity of mineral oil, alkyl benzene, polyalpha-olefin or
alkylated naphthalene lubricants or combinations thereof that would
not otherwise be miscible or soluble with the HFO but is at least
partially miscible or partially soluble when added to the HFO in
combination with a polyalkylene glycol, polyalkylene glycol ester
or polyol ester. Typically, this is a quantity up to about 5-20
weight %, however in some embodiments may range up to 90 weight %.
A surfactant may also be added to compatibilize the mineral oil
with the polyalkylene glycol, polyalkylene glycol ester or polyol
ester and the HFO, as disclosed in U.S. Pat. No. 6,516,837, the
disclosure of which is incorporated herein by reference.
The compositions of the present invention may include other
components for the purpose of enhancing or providing certain
functionality to the composition, or in some cases to reduce the
cost of the composition. For example, the present compositions may
also include a compatibilizer, such as propane, for the purpose of
aiding compatibility and/or solubility of the lubricant. Such
compatibilizers, including propane, butanes and pentanes, are
preferably present in amounts of from about 0.5 to about 5 percent
by weight of the composition. Combinations of stabilizer, and
solubilizing agents may also be added to the present compositions
to aid oil solubility, as disclosed by U.S. Pat. No. 6,516,837, the
disclosure of which is incorporated by reference.
The composition of this invention may optionally include
alkylbenzenes, or hydrocarbon based lubricants in amounts of from 0
to about 30 weight percent.
The fluoroalkene and lubricant forms an immiscible composition
having two or more distinct phases, preferably having a distinct
interface which can be determined either visually or by
refractometry. Provided that the density of each phase is close to
that of the other, the fluids can be easily kept in circulation in
the compression-type refrigeration device. Preferably, the
composition has a refrigerant-rich phase and one or more
lubricant-rich phases wherein the difference in density between the
refrigerant-rich phase and the lubricant-rich phase is about 20% or
less, preferably about 10% or less, and more preferably about 5% or
less.
At temperatures below the "phase inversion temperature" the
lubricant-rich phase is on top of the refrigerant-rich phase and at
temperatures above the "phase inversion temperature" the
refrigerant-rich phase is on top of the lubricant-rich phase. The
temperature at which a particular composition flips from one phase
on top to the other phase on top is the phase inversion
temperature. Usually for temperatures less than the phase inversion
temperature a majority of lubricant floats on top of the
refrigerant-rich phase before the circulation is started. For a
temperature near the phase inversion temperature, stable emulsions
are produced at all flow rates and once produced, the equilibrium
phase separation time is very long, on the order several hours for
complete separation. For temperatures greater than the phase
inversion temperature, the lubricant-rich phase is present at the
bottom of reservoirs, and once flow has begun, a stable emulsion is
created. For vessels or components where the withdrawal piping is
located at the bottom, at temperatures greater than the phase
inversion temperature, circulation rates higher than the charged
composition indicate that conglomeration of lubricant-rich phase
sinks to the bottom of the reservoir where it is drawn again into
circulation. This emulsion and phase inversion temperature behavior
allows the reliable operation of the compression-type refrigeration
device. That is, the composition is in a form wherein either the
refrigerant-rich phase is positioned on the lubricant-rich phase or
the lubricant-rich phase is positioned on the refrigerant-rich
phase, and a temperature exists at which the positions of the
refrigerant-rich phase and the lubricant-rich phase reverse
positions relative to one another. Such phase inversion
temperatures may range from about -15.degree. C. to about
75.degree. C., preferably from about 10.degree. C. to about
60.degree. C., and more preferably from about 20.degree. C. to
about 50.degree. C.
Any of a wide range of methods for introducing the refrigeration
compositions of the present invention to a compression
refrigeration, air-conditioning or heat pump system can be used
from the present invention. For example, one method comprises
attaching a refrigerant container to the low-pressure side of a
refrigeration system and turning on the refrigeration system
compressor to pull the refrigeration composition into the system.
In such embodiments, the refrigerant container may be placed on a
scale such that the amount of refrigeration composition entering
the system can be monitored. When a desired amount of refrigeration
composition has been introduced into the system, charging is
stopped. Alternatively, a wide range of charging tools, known to
those skilled in the art, are commercially available. Accordingly,
in light of the above disclosure, those of skill in the art will be
readily able to introduce the HFO refrigerant and refrigeration
compositions of the present invention into compression
refrigeration, air-conditioning and heat pump systems without undue
experimentation.
EXAMPLE 1
A calorimetric performance test system using a full automotive air
conditioning system utilizing production heat exchangers, lines and
compressor was run using PAG RL897 as lubricant and HFO-1234yf as
refrigerant. There were no oil return problems. This was because of
the surprising emulsion like behavior of the refrigerant/oil
mixture. This is due in part to the similarity in density as shown
by the inversion in density.
EXAMPLE 2
A circulation loop was constructed to investigate the charge
concentration of the loop compared to the circulating composition
at various temperatures for an Idemitsu PAG 46PS/HFO-1234yf
mixture. The apparatus was constructed such that a large reservoir
was drained slowly from the bottom and the liquid was pumped and
returned to the top of the reservoir. The pumping rates were
regulated to traditional automotive system refrigerant flow rates
from 5 to 60 g/sec and the large reservoir was used to simulate an
worse case high pressure side liquid receiver. The results are
shown in Table 1. For temperatures less than the phase inversion
temperature (34.degree. C.) the lubricant-rich phase floats on top
of the refrigerant-rich phase before the circulation is started.
For flows greater than 15 g/sec, the turbulence in the reservoir is
high enough to create a stable emulsion and the circulation
concentration is the same as the charged concentration; while even
for low flow, the circulating flow still contains a very large
percentage of the charged lubricant as the static equilibrium
separation concentration is approximately 4%, but a small amount of
lubricant rich phase is still present at the surface. For a
temperature near the phase inversion temperature, stable emulsions
are produced at all flow rates and once produced, the static
equilibrium separation time is very long, on the order several
hours. For temperatures greater than the phase inversion
temperature, the lubricant-rich phase is present at the bottom of
the reservoir, and once flow has begun, a stable emulsion is
created. The circulation rates higher than the charged composition
indicated that conglomeration of lubricant-rich phase sinks to the
bottom of the reservoir where it is drawn again into circulation,
and is indicative of the experimental setup, whereas in an
operating heat pump, AC or refrigeration system the oil that
travels into a high pressure liquid receiver will flow through and
out of the withdrawal piping and will not be logged vessels or
manifolds.
TABLE-US-00001 TABLE 1 Circulation Rates for Bottom draw of
HFO-1234yf and Idemitsu PAG 46 PS Temperature Temperature
Temperature 20.degree. C. 35.degree. C. 45.degree. C. Min. Flow
Charged: 10.7% Charged: 10.8% Charged: 10.8% Rate Circulating:
Circulating: Circulating: 5 g/sec. 8.9% 16.3% 47.4% Avg. Flow
Charged: 10.7% Charged: 10.7% Charged: 10.8% Rate Circulating:
Circulating: Circulating: 30 g/sec. 10.8% 11.9% 18.8% Max. Flow
Charged: 10.6% Charged: 10.4% Charged: 10.3% Rate Circulating:
Circulating: Circulating: 50 g/sec. 10.9% 11.0% 19.5%
Phase inversion and immiscibility has also been measured with
polyol ester lubricants at temperatures approximately equivalent to
polyalkylene lubricants. Alkylbenzene, mineral oils,
polyalpha-olefins and alkylated naphthalenes have phase inversion
temperatures greater than 70.degree. C. which limits their
application in air conditioning, residential heat pump and
refrigeration equipment; however, these mixtures could have
application in high temperature heat pump applications. The
mixtures of hydrocarbon lubricants such as alkylbenzene, mineral
oil, polyalpha-olefin and alkylated naphthalenes with polyol ester
have phase inversion temperatures between the POE-HFO mixture and
the hydrocarbon lubricant --HFO mixture temperature depending on
the POE-hydrocarbon lubricant blending ratio.
EXAMPLE 3
FIGS. 1 and 2 show the densities of constant concentrations of
HFO-1234yf with two different polyalkylene glycol lubricants, Denso
ND 8 oil and Idemitsu PAG 46 PS, respectively. While the ND 8 oil
and the 46PS lubricants are similar in type classification and
viscosity grade, the base molecules for which the final lubricant
product is constructed are different. The density curves were
experimentally determined by mixing a constant weight percentage of
HFO-1234yf with lubricant and measuring the mixture liquid density
over the range of temperatures from 0.degree. C. to 150.degree. C.
This was repeated for each lubricant--refrigerant ratio progressing
from pure lubricant up to 50% HFO-1234yf. For both lubricants at
the 50% refrigerant-lubricant blend, the liquid solution becomes
immiscible and splits into fluoroalkene rich and fluoroalkene lean
phases. This concentration and for concentrations greater than 50%
fluoroalkene this mixture exhibits a density phase inversion where
the fluoroalkene rich phase becomes lighter than the fluoroalkene
lean phase upon heating. This phase inversion occurs at
approximately 35.degree. C. for the Denso ND 8 oil, while the
Idemitsu PAG 46PS lubricant exhibits a density inversion
temperature from approximately 25.degree. C. and 35.degree. C. that
varies slightly as the refrigerant lean phase concentration
varies.
PROPHETIC EXAMPLES 4-18
The procedure of Example 3 is repeated with the following
refrigerant-oil mixtures which produced acceptable results. Example
4--cis-1,3,3,3-tetrafluoropropene/PAG Example
5--trans-1,3,3,3-tetrafluoropropene/PAG Example
6--1,1,1,2-tetrafluoropropene/PAG Example
7--1,1,1-trifluoro-3-chloro-2-propene/PAG Example
8--3,3,3-trifluoropropene/PAG Example
9--cis-1,3,3,3-tetrafluoropropene/PEG Example
10--trans-1,3,3,3-tetrafluoropropene/PEG Example
11--1,1,1,2-tetrafluoropropene/PEG Example
12--1,1,1-trifluoro-3-chloro-2-propene/PEG Example
13--3,3,3-trifluoropropene/PEG Example
14--cis-1,3,3,3-tetrafluoropropene/POE Example
15--trans-1,3,3,3-tetrafluoropropene/POE Example
16--1,1,1,2-tetrafluoropropene/POE Example
17--1,1,1-trifluoro-3-chloro-2-propene/POE Example
18--3,3,3-trifluoropropene/POE
While the present invention has been particularly shown and
described with reference to preferred embodiments, it will be
readily appreciated by those of ordinary skill in the art that
various changes and modifications may be made without departing
from the spirit and scope of the invention. It is intended that the
claims be interpreted to cover the disclosed embodiment, those
alternatives which have been discussed above and all equivalents
thereto.
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